GB743064A - Improvements in the production of thermoplastic powders - Google Patents

Abstract

Dry powdered thermoplastic material, which does not contain a plasticizer, is heated in intimate admixture with an effect material to a temperature of at least 120 DEG C., but insufficiently high to cause any substantial fusing together of the particles of the thermoplastic material, until mechanical segregation of the effect material from the thermoplastic material has been rendered difficult. The thermoplastic material may be cellulose acetate, cellulose propionate, cellulose acetate-propionate, cellulose acetate-butyrate, ethyl cellulose, benzyl cellulose, nylon 66, polyvinyl chloride, polystyrene or polymethyl-methacrylate. The effect material may be a dye or pigment. The dyes specified include azo, aminoanthraquinone or nitro-aromatic amine dyestuffs, and the pigments include titanium dioxide, barium sulphate, prussian blue, ultramarine, chrome yellow, ferric oxide, indanthrone and its halogen derivatives, flavanthrone, dibenzanthrone and its halogen and alkoxy derivatives, water-insoluble azo dyes from diazo compounds (free from salt-forming groups) and beta-naphthol, acylacetic-arylamides and arylamides of 2:3hydroxynaphthoic acid or ortho-hydroxy-carboxylic acids of the anthracene, carbazole and di-phenylene oxide series, phthalocyanine pigments or acid wool dyes. The heat treatment, which may be at temperatures up to 220 DEG C., may be effected in air or nitrogen, and during the treatment the powder mixture, which may be in thin layers, is continuously or occasionally agitated. The mixture may be obtained by ball-milling dry thermoplastic powder and effect material, by mixing both materials in a liquid which dissolves neither and evaporating the liquid, or by mixing the thermoplastic material with an aqueous or other solution of the effect material, which is not taken up by the thermoplastic material, and evaporating the solvent. The coloured material may be used as a moulding powder or for extruding into sheets, tubes or filaments. Specifications 719,853 and 726,900 are referred to. According to the Provisional Specification a solution or aqueous dispersion of colouring matter may be applied to cellulose acetate fibres, yarns, fabrics, foils or sheets, and the solvent or dispersion medium is removed by drying at 100 DEG C. to 130 DEG C.